Laminated ski



sept, 9, 195s H. E. HOLMBERG EI'AL LAMINATED SKI Filed. Aug. 4, 1955 FwN, NN MN Mm. wm. NN

ww MM U UM "Hulllllllllhllih MIIMVHWIAW:

United States Patent O LAMINATED SKI Hartvig E. Homberg and Harry E.Holmberg, St. Paul, Minn.

Application August 4, 1955, Serial No. 526,881 4 Claims; (Cl. 280-11.13)

This invention relates to skis,and more particularly to skis havinglaminated structure to better bring out good characteristics of skiperformance and construction while minimizing the bad characteristics.

Laminated skis have been known in the prior art for quite some time, andlaminating technique has been used in the case of all-wood skis tolessen the tendency of the ski to warp and to prevent splitting andcracking of the ski along the grain structure. VIn addition, thecurvature of various parts of the ski are more easily obtained whenseparate laminations are dealt with. Such laminated wood skis are lightVand dependable but lack 'in wear resistance and in control during use,particularly when the ski has become slightly worn at the lower sideedges. Ithas, therefore, become customary to insert metal wearing edgesin the form of strips of steel and the like along the bottom corners`and to make such edges sharp by grindingor filing whenever they becomedull from usage. Sometimes when the skis are subject to abuse, the edgestrips or inserts will become loosened, broken or even ripped out. It isdiicult to repair a ski in this condition because the strips have beencarefully inlaid and the ends embedded in the internal structure of` theski.

Other types of laminated skis have been proposed in which wood, metaland plastic laminae have been employed. Here again the wearing edges arereinforced with steel strips so as to maintain a sharp edge during thelife of the ski. The laminated ski structures having combinations ofmetal, plastic and the like with steel edge strips have causedconsiderable trouble in that changes of temperature will cause the skito behave in a manner similar to a bimetallic strip wherein the internalstresses of the laminations having dilerent coefficients of expansionwill create a warping or bending along the length of the ski. Also, thebonded laminae including plain sheets of metal often become loosenedthrough rough usage or temperature changes and cause the ski to lose itsresilience and eiliciency.

The ski construction of the present invention contemplates a laminatedstructure which will overcome the above noted objections, and it is animportant object hereof to provide a ski having different laminatedmaterials eicientlycombined to form a light weight, dependable ski whichis strong and Will not warp under extreme conditions of weather andusage.

It is a further object of the invention to provide a laminated skistructure in which a part of one of the laminations provides not onlystrength and resilience throughout thev length of the ski, but alsoprovides a sharp edge at the bottom side corners.

lIt, is a more specific object of the invention to provide a balancedlaminated structure in which metallic laminations are applied in groupson -both sides of the medial core of material, the grouped laminationshaving such overall corresponding coefficient of expansion as to preventthe ski from warping.

It isa still further object of the invention to provide a laminated skistructure in which at least one of the laminations above the corestructure is constructed from sheet steel, and at least one of thelaminations below the core structure is likewise constructed of sheetsteel and extends outwardly to further function 'as a Wear-resistingsharp running edge.

A still further object of the invention resides in novel steelplate-lamination at the underside of the ski in which the longitudinalrunning groove is bridged by a steel plate selectively perforated insuch manner as to be conveniently formed in recessed manner within thegroove, said perforations also strengthening the bond of the steel plateto the rest of the ski and at the same time lightening the structurewithout sacrificing the aforementioned properties.

These and other objects and advantages of the invention will more fullyappear from the following description made in connection with theaccompanying drawings, wherein like reference characters refer to thesame parts throughout the several views and in which:

Figure l is a plan view of our laminated ski, portions thereof beingsegmentally layered and hidden parts shown in dotted line;

'Figure 2 is a side elevation of the ski;

Figure 3 is an enlarged'rear end segment of the bottom of our skistructure, layers being cut away to better show the internal structureof the ski; hidden portions being indicated in dotted line;

Figure 4 is an enlarged cross section taken on the line 4-4 of Figure l;

Figure 5 is an enlarged cross section taken on the line 5 5 of Figure l;and

Figure 6 is still another cross section taken on the line i 6-6 ofFigure l.

vWith continued reference to the drawing, our ski is shown in overallconfiguration in Figs. l and 2. The ski is laminated and has aconventional shape comprising an upper surface 10, a lower surface 11and side edges 12 and 13. The fore of the ski is turned upwardly at 14and thetrear of the ski terminates in a heel 15. The medial portion ofthe ski 116 is somewhat arched and of thicker dimensions, all `as iscommonly known in the art.

Our invention resides in a particular laminated structure which provideslight and strong construction with long-wearing running edges withoutnecessitating the embedding of individaul wear strips. The body or core17 of the ski is preferably formed of wood and we have found that apressed and bonded material formed of wood particles in which the grainis randomly disposed provides an ideal strong and resilient structure.It is, of course, requisite that a ski have a certain degree ofresiliency, yet must not whip or flex excessively. The core 17 maybesolid throughout, but we prefer that a medial portion 18 be formed as alongitudinal hollow space since the strength of the ski is adequate andthe elimination of the medial material will further lighten the ski. Thepractice of providing hollow cores is also well known in the art.However, we believe that the selection of bonded wood particles ofrandom fiber is an innovation which has not before been discovered inthe art of controlling resilience in ski construction. The core 17extends substantially for the length of the ski and terminatesrearwardly at 19 and preferably short of the overall rearwardtermination 15 of the ski. A heel plate 20 of aluminum or other suitablematerial is positioned in the plane of the rearmost narrow and thin end19 of core `17 so as to give additional strength at this vulnerablearea.

Similarly, the forward and widened terminus 21 of core 17 has a curvedtoe plate 22 which forms the forward continuation of the core 17 and thebody area of I the curved forward end 14 in the completed ski structure.

The heel and toe plates 20 and 22 provide continuations of the sideedges 12 and 13 in a smooth and uninterrupted manner. The toe plate 22is preferably ungrooved, while the heel plate 20 has an upwardly archedgroove 23, as shown in Fig. 5, to match the remainder of the ski, aswill be subsequently described.

In order to improve the appearance of the ski and to provide moreresistant side structures 12 and 13, a thin strip 24, preferably oftough plastic, is bonded to the side edges of core 17, as shown in Figs.3 and 4. The strip 24 may have an outward flare 25 at the bottom thereofto support and register the laminated structure presently to bedescribed. The core 17, thin plastic strips 24, heel plate 20 and toeplate 22 in their proper position all constitute a smooth and continuousupper surface 26 and a lower surface 27, as shown in Fig. 4.

To the upper surface 26 of the previously described core portions of theski is laminated a plurality of sheets designated `generally at 28.Similarly, a plurality of laminations are bonded together and to theundersurface 27 and are generally designated at 29 in Figs. 4, 5 and 6.The upper laminations 28 consist preferably of a hard aluminum sheet 30and preferably within a thickness range of from 0.015 to 0.035 of aninch. This hard aluminum has a rather high coeicient of expansion whichmust be given careful consideration. The heel and toe pieces 20 and 22may be constructed of softer aluminum and their coefficients ofexpansion may vary considerably because of their relatively shortlengths. The aluminum sheet 30 covers the upper surface 26 andpreferably extends to the extreme outer margins of the entire ski. Thesheet may be bonded to the core 17 with a suitable bonding agent ofconventional form. To the upper surface of the aluminum sheet 30 isbonded a spring steel sheet 31. The steel sheet is of tempered carbonspring steel and preferably continuous and imperforate and of athickness range between 0.006 and 0.010 throughout. The steel sheet 31is preferably coextensive with the area of aluminum sheet 30 and overthe entire upper area of the ski. A final layer 32 of hard plasticmaterial such as a hard plastic sheet, preferably of the phenolicthermo-setting type, is bonded to the steel layer 31 with suitablebonding material and, again, the plastic sheet 32 may be coextensivewith the entire area to complete the upper laminated structure 28. Itwill be observed that the split portions of core 17, side strips 24 andthe toe and heel plates 22 and 20 respectively will all be firmly unitedby the bonded layers 28.

As to the laminated layers 29, the innermost sheet layer 33 ispreferably formed of hard aluminum of the same composition and of thesame thickness as aluminum sheet 30. The lower sheet 33 has a side edge34 which preferably extends to each side so as to register with thelower enlarged edge 25 of the side strip 24. A medial longitudinal band35 is bent upwardly to form a running groove throughout the greaterportion of the length of the ski. Bent portion 35 may be convenientlyformed at the hollow space 18 running lengthwise of the core 17. Again,the aluminum sheet 33 may be bonded with suitable bonding material tothe lower surface 27 of core 17 in the manner described.

An important feature of this invention is the steel lamination 36 whichis bonded to the undersurface of alu-l minum sheet 33. The steel sheet36 is also constructed of tempered carbon spring steel and is preferablyslightly thicker than the steel sheet 31 at the upper surface of theski. We prefer a thickness of from 0.015 to 0.030 for the lower sheet.The steel sheet 36 is shown in detail in Fig. 3. Sheet 36 is perforatedthroughout the greater portion of its area and these perforations arediscontinuous in nature, yet will have considerable strength in theintegral sheet. At least some of the perforations 37 are arrangedsymmetrically along the longitudinal band defining the raised runninggroove created by bend 35 in the aluminum sheet 33. The perforations 37are preferably rectangular so as to present outer edges 38 whichregister with the terminal lines of the bend 35 and also providesomewhat weakened bridging strips 39 which are capable of being bendupwardly in the same configuration as the longitudinal bend 35, all asshown in Figs. 3 and 4. Since the area of the bridging strips 39 isrelatively small compared with the total area of the groove 35, thesteel will easily form its bend at each of the strips and be retained inthe groove. Solid Spring steel has a greater tendency to break loosefrom its bonded relation and does not conform as readily to the curvedgroove conliguration.

The remainder of the perforations 40 may be of any convenient form andpreferably are punched in circular openings, as shown in Fig. 3. Theperforations serve to lighten the steel material while, at the sametime, preserving the sheet 36 in integral form. The side edges 41 extendoutwardly to register with the widened area 25 and the outer edges 34 ofthe aluminum sheet 33. The edges 41 constitute a hardened running edgeat each side of the ski and may be sharpened from time to time duringthe life of the ski.

Another plastic sheet lamination 42 is bonded to the underside of thesteel sheet 36 and may be formed of hard plastic material of a phenolicnature such as a hard plastic sheet preferably of the phenolicthermosetting type. The thickness may vary to some degree. We prefer,however, to utilize plastic sheeting of /g of an' inch thickness.

In the technique of bonding the laminations to the core or bodystructure, we employ pressure of pounds per square inch and atemperature of 300 Fahrenheit. In order to prevent squeezing out of thebonding material, we may insert a spacing material between any of thecontiguous metal sheets, as typified by the cheesecloth layer 43 betweenthe metallic layers 33 and 36. The cheesecloth will thus maintain asuiiicient amount of bonding material between the metallic surfaces toachieve a strong union. The cheesecloth 43 will squeeze into theopenings, as shown in Fig. 3, and carry an amount of bonding materialwith it so as to unite the layers not only in surface relationship butalso in continuous form through the openings.

The upper laminations 28 and the lower laminations 29 are selectivelybalanced so that the overall coeicient of expansion due to changes intemperature will distribute stresses equally and not cause warping orbending during changes in the weather. The continuous steel layer 36 iscounter-balanced by the upper steel layer 31 and the integral quality ofthe sheet 36 is such as to positively prevent separation or loosening ofthe running edges 41 and is also so designed in a light structure tointeriit in permanent relation with the desirable center running groove.

The particular type of multiple upper and lower laminations combinedwith a `bonded wood particle core in which the fibers are randomlydisposed gives a properly resilient ski structure which is damped to theproper degreevto prevent chattering or vibrating during use.

It will, of course, be understood, that various changes may be made inthe form, details, arrangement and proportions of the parts withoutdeparting from the scope of our invention.

What we claim is:

1. In a laminated ski construction, a hard continuous metal sheet bondedat the underside of a ski having a lengthwise groovev formed therein,said sheet having discontinuous perforations formed through the surfacethereof for the greater portion of its length, at least some of saidperforations defining a weakened longitudinal zone medially of the skiconsisting of a plurality of bridging strips extending completely acrosssaid lengthwise groove and bent upwardly thereinto, and a runningsurface bonded to the lower face of said perforated metal sheet, saidmetal sheet traversing the width of the ski and terminating laterally ateach side in exposed running edges.

2. In a laminated ski construction having an upwardly formed runninggroove in the lower surface thereof, a continuous steel sheet bonded atthe undersurface thereof, said sheet having a plurality of discontinuousperforations formed therethrough for the greater portion of the lengthof said sheet, at least some of said perforations being of such width asto define a plurality of bridging strips extending across at least thewidth of said running groove and defining a weakened longitudinal zonemedially of the ski, said plurality of bridging strips Ibeing spacedlongitudinally of, and `bent upwarly into,

said running groove, and a running surface `bonded to the lower face ofsaid perforated steel sheet, said sheet traversing the width of the skiand terminating at the bottom corners respectively in exposed runningedges.

3. A laminated ski comprising, an elongated core element having upperand lower surfaces and provided with a substantially medially disposedand longitudinally extending slot, a plurality of sheet laminae bondedtogether and to the upper surface of said core element and bridging saidslot, and a plurality of sheet laminae bonded together and to the lowersurface of said core element and bridging the aforementioned slot, theupper lamina comprising an aluminum sheet bonded directly to the uppersurface of said core, a spring steel sheet bonded to the upper surfaceof said aluminum sheet and a hard plastic sheet bonded to the exposedupper surface of said spring steel sheet with all of said sheetsextending the full width of said core and being continuously exposedalong their longitudinal edges at opposite sides of the core, the lowersheet lamina comprising an aluminum sheet bonded directly to theundersurface of said core, a spring steel sheet bonded directly to theundersurface of the last mentioned aluminum sheet and a hard plasticsheet bonded directly to the undersurface of the last mentioned springsteel sheet, the last mentioned aluminum sheet being arched upwardlyalong a longitudinal medial portion thereof to be disposed within theconines of said slot in the core and the underlying spring steel andplastic sheets being correspondingly deformed upwardly, and said lowerspring steel sheet being formed in the longitudinal medial portionthereof directly in register with said slot with a plurality ofsubstantially rectangular and closely spaced openings defining arcuatedbridging strips therebetween whereby a relatively small area of themedial portion of said lower spring steel sheet is deformed upwardlybeneath the arched central portion of said lower aluminum sheet.

4. A laminated ski comprising, an elongated core ele ment having asubstantially medially disposed groovedefining recess extending for thegreater portion of Ithe length of said ski, a plurality of upper sheetlaminae comprising a sheet of aluminum and a sheet of spring steelbonded together and to the upper surface of the core, and a hardexternally exposed plastic sheet bonded in uppermost overlyingrela-tion, a plurality of lower sheet laminae comprising a sheet ofaluminum and a sheet of spring steel bonded together and to the lowersurface of the core, and a hard externally exposed plastic sheet bondedin lowermost underlying relation, said sheet of spring steel in thelower sheet laminae having a series of openings formed longitudinally ofthe sheet and each opening defining with an adjacent opening a lateralbridging strip, said aluminum and said steel sheets of the lower laminaebeing deformed upwardly to provide a longitudinal groove within saidgroove-dening recess, said bridging strips extending at least across thefull width of said groove and thereby reducing the area of the steelsheet which is deformed.

References Cited in the file of this patent UNITED STATES PATENTS2,184,791 Broome Dec. 26, 1939 2,490,549 Schultz et al. Dec. 6, 19492,560,693 Hickman July 17, 1951 2,581,532 Hem Ian. 8, 1952 2,694,580Head Nov. 16, 1954 2,695,178 Rheinfrank Nov. 23, 1954 2,791,435 MelandMay 7, 1957 FOREIGN PATENTS 631,879 Great Britain Nov. 11, 1949 979,589France Dec. 13, 1950

